Plaster of Paris supported on fabric or gauze has been used almost exclusively in the preparation of surgical casts designed to immobilize and support portions of the body, e.g. a leg arm, wrist, neck and the like. Plaster of Paris is inexpensive, convenient and ready to use after simply dipping in water. Moreover, practically all physicians, particularly orthopedic specialists, have long worked with the Plaster of Paris medium and are very familiar with the application. Once having mastered the art of working with plaster of Paris they are reluctant to learn the different techniques associated with other media.
Notwithstanding, plaster of Paris has certain shortcomings. It is relatively heavy and can be damaged by wetting with water. It is also substantially opaque to x-rays, thus sometimes requiring that a cast be removed to ascertain, for example, whether a fracture has satisfactorily healed.
The various aforementioned problems with plaster of Paris orthopedic bandages have led to the development of orthopedic bandages such as the bandage described in U.S. Pat. No. 3,630,194. This bandage utilizes as a cast forming composition a mixture including a water soluble monomer selected from the group consisting of DAA, N-IPA and mixtures thereof, said monomers being polymerizable, in the presence of water, by means of a redox catalyst system which comprises an oxidation component and a reducing agent. This bandage is hardened in a manner similar to the prior art plaster of Paris bandages by dipping the bandage into tap water. The advantage of this method of initiation is that, unlike certain other bandages which use thermoplastic sheets or apply hardenable resins from a paste, the technician working with the bandage does not have to learn new techniques for preparing a cast.
Although satisfactory in many ways, it has been found that the orthopedic bandages described in U.S. Pat. No. 3,630,194 suffered from certain drawbacks. For example, the rate of hardening was found to vary with the different tap waters used to initiate the polymerization reaction. Investigation of this phenomena surprisingly led to the discovery that the presence of different impurities in the tap water, such as copper led to the non uniform rates of hardening.
Furthermore, when both the oxidation and the reduction components of the catalyst were packaged in the cast forming composition, as opposed to adding one or both of the components in the tap water, storage stability was found to be lacking.
These problems have now been solved in the novel orthopedic bandage of this invention.